Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Stents are generally tubular in configuration, open ended and are expandable between a generally unexpanded insertion diameter and an expanded implantation diameter. Stents are commonly placed or implanted by a mechanical transluminal procedure.
Inflation expandable stents are well known and widely available in a variety of designs and configurations. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is concerned with balloon expandable stents, self expanding stents and/or hybrid stents.
An example of a stent is described in PCT Application NO. 960 3092 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.
U.S. Pat. Nos. 4,733,665; 5,019,090; 4,503,569; 4,512,338; describe various stent configurations. U.S. Pat. Nos. 4,732,152 and 4,848,343 describe self-expanding stents.
Stents have been made using materials of varied composition and conformation. U.S. Pat. No. 4,768,507 describes a stent constructed of stainless steel, and a titanium alloy. U.S. Pat. No. 4,820,298 describes a stent having a flexible tubular body made from a thermal plastic to the form of a helix. Polyester and polycarbonate copolymers are selected as particularly desirable materials. U.S. Pat. No. 4,830,003 describes a stent made from wires formed into a cylinder. The wires are made of a biocompatible metal. Biocompatible metals include 300 series stainless steels such as 316 LSS, as well as platinum and platinum iridium alloys, cobalt chromium alloys such as MP35N, and unalloyed titanium. U.S. Pat. No. 4,886,062 describes a stent made from low memory metal such as a copper alloy, titanium, or gold. U.S. Pat. No. 4,907,336 describes a wire stent having malleable materials such as annealed stainless steels, tungsten and platinum in its construction.
Canadian Application 2,025,626, describes a bio degradable infusion stent of extruded material. The stent may incorporate radiopaque materials such as barium sulfate. U.S. Pat. No. 4,990,155 describes a plastic stent having an inherently expandable coil conformation. Materials of construction include high density polyethylene. Optionally, this material is compounded with an anti coagulant and/or an x ray opaque material such as bismuth sub carbonate. Canadian Patent Application 2,008,312, describes a stent made from a malleable flat sheet having a reticulated pattern.
There are also stents which deliver agents or drugs to blood passing through the vein or artery that are generally beneficial to the recipient. In addition, stents can deliver drugs or biologically active agents at a controlled rate to blood passing through the vessel lumen as well as to the vessel wall. U.S. Pat. No. 5,234,456 describes a hydrophilic stent comprising a wall structure where at least a portion thereof is a hollow wall in which a hydrophilic material for drug delivery is placed. U.S. Pat. No. 5,443,458 is directed to a multilayer laminated resorbable stent having a structural layer and additional layers stated to release drugs at predictable rates. U.S. Pat. No. 5,258,020 describes a self-restrained stent with an elastic memory, the stent optionally being formulated to provide for drug administration.
Some medical devices such as stents may be provided with a coating. The coating may enhance or alter the performance characteristics of the medical device. In some cases the coating may be a drug, wherein the stent is used to deliver the drug coating directly to a location in a body lumen or vessel. A coating may be applied directly to a medical device or portion therein. Some devices include a reservoir or other feature which is specially designed to receive the drug and/or coating. In some cases a drug and/or coating may be applied to selected portions of a stent by masking features of the stent where it is undesired to provide the drug and/or coating.
It is known that in some cases, when stents are in the reduced state prior to delivery, components of the stent may be pressed together and may contact one another. Stent components may also come into external contact with various elements of a delivery catheter such as the catheter shaft, an external sheath, sleeve or sock, or other catheter components. Contact between stent components or contact between the stent and catheter components may result in a coating, particularly a drug coating, being broken off, rubbed away or otherwise impaired or damaged.
In some embodiments, the coating used on a stent, or a portion thereof, may be characterized as having a sticky or adhesive quality. When such a coating is present on stent components that may come into contact with one another, or when such coated components contact components of the catheter, the respective components may adhere or stick together with potentially detrimental effect to the stent, catheter, and/or the patient.
As a result, it is desired to provide a stent, or a portion of a stent with the capacity to be coated, wherein elements of such a coated stent are prevented from sticking together to ensure uniform expansion of the stent and to protect the drug coating from damage. It is further desired to provide a means for reducing or preventing contact between coated portions of a stent and other adjacent portions of the stent or potions of the delivery catheter or device.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The invention in various of its embodiment is summarized below. Additional details of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
The abstract provided herewith is intended to comply with 37 CFR 1.72 and is not intended be used in determining the scope of the claimed invention.